| | Genetic Sources and Potential of 21st Century Triticale Germplasm: Past, Current and Future Breeding Goals, Achievements and Limitations
The synthesis and genetic structure of triticales - there are many kinds
Since the very first hybridized triticale was made from crossing rye and wheat in 1876, many more triticales have been synthesised. This has resulted in this novel species (non-existent in the wild state) becoming suitable for cultivation as a crop for many different purposes. Some of the earliest work that actually resulted in varieties of commercial value was conducted at the University of Manitoba from the mid 1950’s to the early 1960’s, with the variety Rosner being the first triticale released in N. America. Since that time Canadian breeding research has endured varied levels of support, including termination of the Manitoba program, but longer term commitment evolving at Lacombe, Alberta (funded by the Alberta Government) and at Swift Current funded by Agriculture and Agri-Food Canada (AAFC).
Triticales are synthesised by crossing rye either with tetraploid (durum) wheat or with hexaploid (bread) wheats, to create triticales that are hexaploid or octaploid, respectively. The summary chart from Simmonds (1976) in Figure 1 concisely compares the many different kinds of triticale which exist, and describes their varied chromosomal constitution.
Figure 1. The evolution and origins of triticale (Simmonds, 1976)
Hexaploid triticale has proven to be the most successful commercially, to date, and most breeding and research continues with this type because of its superior vigor and reproductive stability compared to the octaploid type. Primary hexaploid triticales therefore have 28 chromosomes from the durum wheat (genome AABB), plus 14 chromosomes from the rye parent (genome RR), for a total 42 chromosomes, but they lack the DD chromosomes from a different species, which donated the bread quality genes to breadwheat. By contrast, the octaploids have 56 chromosomes, 42 from wheat (AABBDD), plus 14 from rye (RR). The octaploids therefore often have better breadmaking quality, but often prove to be unstable in field performance, as well as suffering from genetic instability that leads to floret sterility.
The products that arise from the initial combining of the genomes of rye and wheat, unmodified by further hybridization, are described as Primary triticales. The production of these primary triticales is a rather difficult and slow breeding procedure, and almost no new primary triticales have been produced in Canada since the termination of the Manitoba program. However, a wider array of primary triticales has been produced in other programs internationally since then, and these are almost all represented in the international breeding centered at CIMMYT, Mexico as part of the CGIAR (Consultative Group on International Agricultural Research) research network. CIMMYT also continues to create new primaries, but none are now made in Canada. Both Eastern and Western Europe has been active in primary production, as well as Australia. Primary triticales, however, always require substantial breeding work to remove the problems which they express. These problems generally include partial floret sterility, shriveled seed, low yield potential, poor adaptation to local production conditions, and poor agronomic characteristics. These problems in primaries continue to occur despite recent efforts to pre-breed the rye and wheat parents to seek complementary genes in the two planned parents. In many cases desirable genes from both parents are known to be present in the new primary triticale (as assessed by use of DNA probe technology), but the genes do not express at a suitable level, or may not express at all.
Because of these problems with primaries, breeders started to intercross different primaries, and also cross them with wheat, to seek improved expression of desired traits. The products from this approach are called Secondary triticales, and have new combinations of rye and wheat chromosomes. These types are the most common commercial triticales worldwide, including all Canadian varieties so far released. The only significant production of octaploid primary triticale is believed to be limited to China.
According to the complement of rye chromosomes present, a particular triticale might also be ‘Complete’ or ‘Incomplete’. ‘Completes’ are those where the triticale retains unchanged all of the chromosomes from the rye parent. Generally these types retain much of the robust adaptation characteristics desired from the rye parent, and thrive under conditions where rye is well adapted, such as sandy soils, at high elevations, under high rainfall, or in droughty or soil acidic conditions. Thus, ‘complete’ triticales tend to be the type of choice for superior plant growth in marginal agricultural areas, where other crops including wheat may not perform well.
Two of CIMMYT’s complete triticales, Beagle and Drira, are progenitors of many of the present day commercial varieties grown in Australia, Spain and various third world countries, and appear in the background of many breeding populations distributed worldwide. Another important ‘complete’ triticale that features in many pedigrees is the winter variety Lasko, bred and released in Poland.
‘Substituted’ triticales are those in which the rye chromosome 2R has been replaced with the wheat chromosome 2D from breadwheat. This important change allows for an improvement in bread-making quality in triticale, and was also associated with a solution to the problem of seed shriveling and floret sterility of early triticale varieties. The source for this change was through the variety Armadillo, the product of a naturally occurring outcross from wheat into triticale at CIMMYT.
Under non-stressed conditions the 2D/2R substituted types generally perform better than other triticales. They tend to mature earlier and may be better for bread-making, and offer better prospects for improvement in dough strength from the flour. Unfortunately, the chromosome also contributes a sticky dough characteristic that can be very detrimental for products made in high throughput mechanized processing facilities. Other substituted chromosome types also exist, including the 6A/6D wheat chromosome substitution, which introduces improved bread-making quality, but with all the rye chromosomes still present. This type is found in some CIMMYT materials, as well as in some European winter types.
In many cases where triticale has been backcrossed extensively to wheat, this may result in elimination of some or all of the rye chromosomes, or in retention of only parts of the rye chromosomes which may have translocated (attached) themselves to the wheat chromosomes. These types are sometimes described as ‘Partial’ triticales. Without cytological analysis it is not possible to know the chromosomal composition of a particular triticale line in a breeding program, as it could be ‘complete’, ‘incomplete’, ‘substituted’, or ‘partial’. When a cross is made between triticale lines, it could be between parents that individually might carry a complete rye genome, or only a small part of it. As might be expected, the more that triticale is backcrossed to a wheat parent, usually to recover an improved grain quality type, the more the progeny performance resembles that of the original wheat type, as more rye genes and alleles are eliminated. As far as the author of this report is aware, the specific chromosomal constitution of all current Canadian triticales has not been characterized, although most are believed to be complete hexaploids.
The quality characteristics of older and modern varieties are different
Triticale was originally envisaged as a way to combine the excellent field adaptability of rye to marginal conditions with the yield potential and high grain quality of wheat. In most parts of the world full expression of both parts of this ambition has not been achieved, despite major progress on both fronts. Also, since the initial concept was determined, a large number of the earlier breeding programs have now been discontinued, especially after the 1970’s and 1980’s. Programs were discontinued usually because of slow progress in improving the floret sterility problem (which reduced yield potential), and the seed shriveling problem (which reduced value in feed and milling, and the food quality potential). Much of the earlier literature on grain quality was based on research using varieties that had problematic grain characteristics (shriveling, sprouting, low test weight, high alpha-amylase content etc.), problems that are not now as important in modern varieties as the result of genetic improvements from breeding.
For the reasons outlined above there is now a need to repeat much of the earlier grain quality and use research using modern varieties, to establish the extent to which earlier negative attitudes towards market adoption of triticale are no longer valid. New triticales have grain quality characteristics that are suitable for many grain markets. Lack of production acreage in Canada has been a disincentive for renewed research on this. Basic research on quality specifications for new or potential triticale grain markets is beyond the scope and capacity of the two remaining Canadian breeding programs, but both are limited in breeding scope in the absence of this information. Specific gaps in market quality information are considered later in this report.
Solving the initial problems in triticale - internationally and nationally
The initial Canadian cultivars from the University of Manitoba program (Rosner, Welsh) had many agronomic and grain quality deficiencies, and proved inadequate to meet a grain market in Canada for either feed or food. They were not initially evaluated for potential as forage. On the production side they failed because yields were not competitive with other feeds (e.g. barley, feed wheat) or for food (e.g. wheat). They were late maturing, tall and lodging prone, with a high degree of floret sterility (and subsequent ergot occurrence), and had shriveled grain, low test weight, and prone-ness to post-harvest sprouting, that all detracted from milling quality. On the plus side, grain had high lysine availability, and food products from triticale had a novel, desirable, nutty flavor that appealed to taste panel members. These first triticales also appeared to have (except for ergot susceptibility) a good level of resistance to prevalent cereal diseases and races in W. Canada, which is still the case in 2001.
The original gene pool for the University of Manitoba primary triticales was relatively narrow, and did not involve a wide range either of rye parents or wheat parents. Also, there was no reported pre-breeding of potential parents, to seek specific complementary traits from the wheat and rye for creating the primaries. As a result, the range of genetic variation in the total program was limited, and subsequent breeding potential by selection was consequently limited.
By the time the new fertile, high test weight, non-shrunken seed, semi-dwarf types emanated from CIMMYT, which was creating a far broader range of primaries than in Manitoba, the latter program had virtually closed down, both for basic and breeding research. Continuing Canadian programs then relied almost completely on accessing triticales from CIMMYT, or other non-Canadian programs, selecting from them lines that were best adapted to northern conditions. Germplasm and parent exchange with CIMMYT has been extensive, and still continues. Also, breeding moved extensively to the production of secondary triticales, including backcrosses to wheat, still continuing at AAFRD (Lacombe) and AAFC (Swift Current). The massive improvement in triticale grain quality that occurred in the 1980’s is evidenced in the improvement of test weight that occurred in entries in CIMMYT’s outreach nurseries in this period (Figure 2 from Anon, 1989).
Figure 2. Test weight improvement in CIMMYT triticales – 1970’s to 1980’s
In this same period, improvement in potential baking quality was also achieved (Pena and Balance, 1989) to where loaf volume nearly equivalent to those of the best Mexican wheat cultivars was achieved with many triticale lines. However, triticales worldwide would still be rated as having weak gluten, compared to international breadwheat quality standards, and suffer from ‘sticky gluten’, that requires blending with wheat flour up to a maximum 30% to avoid problems in continuous process breadmaking plants. The ‘sticky gluten’ problem remains to be solved. The weak gluten is a negative in the breadmaking market, but is a plus in other flour product markets (see later section on triticale flour quality).
Because of the major improvements in triticale achieved by breeding in the 1980’s, and subsequent improvements both in feed and food potential, much of the earlier published data about triticale grain quality is irrelevant for modern varieties, as their grain properties are much improved. Thus much of the earlier processing quality and feed research work needs to be repeated using the improved, modern varieties. In most cases very little of this revisiting of the research with new varieties has happened, especially in Canada. To re-establish the specific advantages of triticale grain for Canadian processing and feed opportunities it is imperative that this work be initiated and completed as soon as possible, to determine the real potential for modern Canadian triticale varieties in the modern marketing situation. Results from this will indicate where the priorities for grain quality improvement by further breeding should then be placed.
The improvements in grain quality of triticale have occurred worldwide, and it is useful background information to compare the international breeding priorities of the mid 1980’s with those of today, as is done in the following sections of this report. Many of the issues of that era are still limiting more extensive adoption of triticale in competition with other cereal crops, worldwide and in Canada.
International triticale breeding, issues and adoption - the mid 1980’s situation
In 1986, Varughese (CIMMYT Research Highlights, 1985, CIMMYT, Mexico) presented a review highlighting the advantages of triticale as a crop for marginal environments. International recognition of this wide adaptability resulted in active European breeding programs at that time in Bulgaria, former Czechoslovakia, E. Germany, France, Greece, Hungary, Italy, the Netherlands, Poland, Portugal, Romania, former Soviet Union, Spain, Sweden, UK, and Yugoslavia. Most of these programs are still active, plus others in Asia, S. America, the USA, Canada and Australia.
Some of the special features of triticale that were attractive enough to merit active programs were as follows, and are still valid. Many of these advantages can be expressed under Canadian conditions. In Poland adaptability to acid soils, to replace rye, was noted, including winter types with especially good resistance to mildew and rusts. Also, the special amino acid composition suited for monogastric feed (for pigs and chickens) was a proven advantage. Research to solve quality problems to gain entry to the bread market was a high priority. In the Soviet Union yields >20% more than wheat were obtained, with 1-2% higher protein content, and special adaptability to arid conditions, with salt tolerance and high forage potential was noted. In Portugal CIMMYT lines performed well on acid soils and in arid conditions. In Africa triticale yields were superior to wheat under marginal conditions, up to 100% higher than wheat in some conditions (a result confirmed by the author of this report when in Kenya, 1981-1983, especially on acid soils). Brazil was a major adopter of triticale, which was fully integrated into the bread flour stream for marketing. Their varieties were all based on selection from CIMMYT introductions. The Brazilian advantage was seen in adaptation to acid soils, and in disease resistance to scab, Septoria and Helminthosporium. Australia reported a high adoption level for the improved varieties, for use in feed for sheep, cattle, poultry and pigs, and for forage. Triticale outperformed wheat on marginal and arid conditions and on acid soils, and a limited food market was developing slowly.
Thus by 1986 the special agronomic characteristics of triticale were being recognized worldwide, and the crop was seen as one worthy of further research investment, especially to improve market quality traits. This optimism resulted in more than a doubling of world triticale acreage between 1986 and 1991/92 (Table 1). Specific breeding needs of international concern, that needed improving, were seen in 1986 as follows:
1. Broaden genetic base, both from rye and wheat
2. Improve disease resistance of all kinds (regionally specific needs)
3. Further improve adaptation to acid soils (need rye level) and other stresses
4. Seek earlier maturity (shorten post-flowering period) especially for grain types
5. Repartition assimilates from vegetative parts to grain (higher harvest index)
6. Further eliminate grain shriveling, and achieve test weight equal to wheat
7. Improve lodging resistance, including semi-dwarf development
8. Reduce post-harvest sprouting in wet regions, and reduce grain bleaching
9. Identify anti-nutritional components, that limit feed intake
10. Do extensive feeding trials on specific classes of livestock and animals
11. Eliminate ‘sticky dough’ problem, so triticale can be used in baked products
Most of the above list are still on the priority lists of today’s breeders (see later section of report), although many of the traits have already been greatly improved. Some of the topics have received almost no research attention since the mid-1980’s (e.g. anti-nutritional components). Also, the limited reference to forage potential prior to the 1986 reports highlight the newness of this area of end-use research.
The Varughese review also highlighted issues that affected adoption of the crop, some positive and some negative, that are still valid in 2001. In the food market triticale was seen as a replacement for wheat (and therefore at a disadvantage due to lack of supply and familiarity). Low price could promote use, but not production. On the plus side special flavor characteristics could be exploited, for cookies, bread, baked goods and crackers, particularly for small operations where ‘sticky gluten’ problems could be avoided. The limited published nutritional data confirmed that triticale had a high nutritional value, particularly high in amino acids and vitamin content, compared to wheat. P and K content were also usually higher than wheat, as well as Na, Mn, Fe, and Zn. In addition, digestible energy of triticale was reported as similar to wheat (14.1 and 14.4 MK per kg, respectively), lysine availability was higher than wheat and other cereals, and biological value was 15-20% higher than wheat when evaluated in living animal tests.
Some typical nutrient characteristics of triticale vs other cereals are presented in the following tables. The superiority of triticale lysine content over wheat has been repeatedly reconfirmed worldwide, including data (Table 4) reported by the National Research Council of Canada (NRC, 1989). This trait alone makes triticale of nutrient interest for monogastric animal diets.
Table 3. Amino Acid Content in Triticale, Wheat and Rye (CIMMYT Laboratories, 1982)
 | Triticale
(Yoreme) | Wheat
(INIA) | Rye
(Snoopy) |
| Amino acid | g per 100g protein |
| Lysine | 3.44 | 2.83 | 4.02 |
| Threonine | 3.55 | 2.98 | 4.06 |
| Methionine* | 1.28 | 1.42 | 1.35 |
| Isoleucine | 3.45 | 2.68 | 3.70 |
| Leucine | 7.20 | 7.22 | 7.75 |
| Phenylalanine | 4.94 | 3.77 | 4.74 |
| Valine | 4.48 | 3.73 | 5.10 |
| Tryptophan | 1.20 | 1.10 | N/A |
| * Partial destruction during hydrolysis |
Table 4. Amino Acid Content of Triticale and Some Other Cereal Grains (NRC, 1989)
| Lysine | Threonine | Methionine | Leucine |
| Triticale | 3.4 | 3.6 | 1.3 | 7.2 |
| Wheat | 2.8 | 3 | 1.4 | 7.2 |
| Rye | 4 | 4.1 | 1.4 | 7.8 |
| Barley | 3.6 | 3.5 | 1.5 | - |
| Corn | 3 | 3.5 | 1.5 | - |
| Data in g/100g crude protein |
Table 5. Vitamin Content (Dry Basis) of Triticale, Wheat and Rye (From Michela and Lorenz, 1976)
| Triticale
(Winter type) | Triticale
(Spring type) | Wheat | Rye |
| TR383
µg g-1 | 6TA204
µg g-1 | Chris
µg g-1 | Prolific
µg g-1 |
| Thiamine | 9.8 | 9 | 9.9 | 7.7 |
| Riboflavin | 2.5 | 2.5 | 3.1 | 2.9 |
| Niacin | 17.9 | 16 | 48.3 | 15.3 |
| Biotin | 0.06 | 0.07 | 0.06 | 0.05 |
| Folacin | 0.56 | 0.77 | 0.56 | 0.49 |
| Pantothenic acid | 9.1 | 8.3 | 9.1 | 3.4 |
Table 6. Per Cent of True Protein Digestibility, Biological Value, and Net Protein Utilization of Some Varieties of Triticale Compared with a Wheat variety, Using Male White Rats (Hulse and Laing, 1974)
| Triticale | Wheat |
Mapache | Beagle | PC-297 | Hermosillo-77 |
| True protein digestibility | 92.7 | 91 | 91.5 | 92 |
| Biological value | 66.1 | 69.9 | 59.3 | 57.6 |
| Net protein utilization | 61.3 | 63.7 | 54.2 | 52.9 |
A number of potential anti-nutritional compounds were also known in the mid-1980’s to occur in triticale, but at much lower levels than found in rye, although quantified relevant data is not readily obtainable. Although extensive data are reported on protein and nutritive values of triticale, in the IDRC Report of 1974 (Hulse and Laing, 1974), such data are based on the earlier triticales that, as described earlier, suffered from shrunken kernels and had many other properties different from improved, modern varieties. New data are needed on these characteristics, from the modern varieties grown under Canadian conditions. Candidate problem compounds that may block full use of nutrients include water-soluble pentosans, enzyme inhibitors, alkyl-resorcinols, tannins, acid-detergent fiber, pectins, and protein-polysaccharide complexes. To this author’s knowledge the levels of some of these compounds in Canadian triticale varieties are still not known, in comparison to content in other Canadian feed grains.
In the 1986 reports, a minimum yield improvement of +15% over wheat was seen as necessary to compete with wheat as a feed, especially for monogastrics, even though the high lysine content would mean a lowered level of protein supplementation was needed in the ration. On-farm, successful use of triticale as a complete substitute for either wheat or corn was reported for monogastrics, including swine, quail, chickens, broiler turkeys and tom turkeys, and in the latter case improved meat tenderness was recorded.
In the mid 1980’s new applications of triticale use appeared including forage use in many forms in springs and winters, as cover crop for erosion control, as an awnless annual forage, and as a break crop in sustainable cropping systems. Thus, even internationally, these forage use applications are very new, and AAFRD, Lacombe was a main leader in the forage work, and in the addition of forage potential as a breeding objective. These aspects are reviewed later. However, because of limited subsequent basic research on triticale as a forage, few useful guidelines are available even to today’s breeders that could help them improve forage quality in new varieties, or that could be applied in the selection programs. There is very little progress on the topic of specific forage quality breeding objectives internationally in the last 20 years.
Since 1986, relatively few research trials have been conducted that lead to clear breeding objectives for triticale quality improvement. This topic is further reviewed in the market use sections of this report.
Summary reports describing international breeding objectives and progress since 1986 have been regularly presented at the International Triticale Symposia, including those held in Sydney, Australia (1986), Passo Fundo, Brazil (1990), Lisbon, Portugal (1994), and Red Deer, Canada (1998).
International triticale breeding - the situation in 1998 (4th Int. Triticale Symposium reports)
The most recent systematic review of world-wide applied triticale breeding programs occurred in 1998 at the 4th International Triticale Symposium, Red Deer, Alberta. A summary table (Oettler, 1998) indicated the possible genetic sources for future breeding improvements, for short-term, middle-term, and long-term goals. In comparison to this table, it should be noted that both Canadian breeding programs have already focused for some time on the methods that were judged by Oettler’s classification as ‘highly beneficial’, with little or no emphasis on other approaches. This is a sound strategic approach for applied programs with limited budgets.
Table 7. Introduction of Genetic Variability and its Benefit for Applied Triticale Breeding (From Oettler, 1998)
| Expected benefit |
| Route of introduction | Short-term | Middle-term | Long-term |
| Primary triticale |
| 8x | - | + | + |
| 6x | - | + | + |
| Secondary triticale |
| 8x | - | - | + |
| 6x | ++ | ++ | ++ |
| 4x | - | - | + |
| Primary x secondary triticale | + | ++ | ++ |
| (Triticale x wheat) x triticale | + | ++ | ++ |
| (Triticale x rye) x triticale | - | + | + |
| Triticale with alien cytoplasm | - | + | + |
| Alien species, introgression | - | + | + |
| Mutagenesis |
| Chemical and physical agents | - | + | + |
| In vitro culture | - | + | + |
| ++ Highly beneficial, + Beneficial, - No benefit |
Several interesting breeding goals in countries other than Canada were evident. In Australia, Darvey (1998) indicated a long list of potential goals related to product end-use improvement, for feed grain, forage use, human food (mostly targeting wheat replacement), and industrial uses. This extensive list is presented here, for reference. Darvey suggested that the key to greater global adoption of triticale would lie in achieving suitable bread quality improvement. (This is not true for the N. American production situation, where replacement of wheat in mainstream applications is not a sensible goal. Author). Darvey’s list (modified) is as follows:
1. Animal feed and forage factors:
Protein content/quality; Nutritional and anti-nutritional properties; Vegetative and grain biomass/yield and quality; Test weight; Grazing recovery;
2. Human food (e.g. as wheat replacement):
Grain color, flour color, and bread color; Bread crumb structure; Palatability; Starch content and composition; Fiber content; Gluten quantity/quality; Extensibility; Stickiness; Grain hardness/softness; Non-starch polysaccharides, etc.; Specific variety uses for specific processed products, replacing wheat;
3. Industrial applications:
Bio-ethanol production from triticale carbohydrates; High amylose types for plastic production; Pentosans for glues; Straw strength for thatching, building materials, packaging materials, and straw board;
4. Environmental conservation applications:
Weed control and soil stabilization; Re-vegetation; Reduced herbicide and pesticide use; Improved water use efficiency; Break crop, including extension of rotations;
Darvey (1998) drew particular attention to long-term research potential for three grain quality characteristics, that would likely require dedicated pre-breeding in rye or wheat for the production of new primary triticales:
a. High starch yield, for starch extraction, and high amylose types (of importance for replacing maize, in the Australian situation)
b. Waxy and low amylose products, for their stickiness and flavor enhancement properties
c. High amylopectin (and low pentosan levels for monogastrics), to increase feed conversion
Several other reports at the 1998 symposium (including reports from Australia, and CIMMYT) also reconfirmed effective on-farm use of triticale grain as an un-supplemented grain for swine feeding, confirming achievement of satisfactory nutrient balance for some monogastric animals in current varieties.
Successful production of hybrid triticales targeting higher yields was reported by several authors (including those from Poland, Australia and CIMMYT) with grain yield hybrid vigor of more than 20% over the best parent (Pfeiffer, 1998) in experimental plots using hand crossing or CHA’s (chemical hybridizing agents) to produce the F1 seed. Canadian programs may need to consider this approach in the longer term, for achieving higher yield potential (both for forage and grain) in the future, especially if the lower cost CHA approach to making F1 seed can be used. One disadvantage to use of the CHA system is that it is a patented application, so that products from its use may not be free from license charges. Other systems to make hybrids are available, such as the CMS (cytoplasmic male sterility) system in the public domain, but they result in more costly hybrid seed, and it is doubtful that this will be a feasible economic breeding approach until triticale acreages and annual seed sales would be very much larger. Also, there is evidence (Salmon, 2001, pers.comm.) that the restorer genes for the Triticum timopheevi cytoplasmic male sterility may not be very effective under C.Alberta conditions. On the contrary side of this argument it should be noted that hybrid wheat production in the USA using the CHA system has become minimal since the owner of the technology of the best CHA chemicals (HybriTech) discontinued business (Pers. comm. Dr. Joe Smith, AgriPro, Feb. 2001).
Report prepared March 2001 |
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